Speedability

Add a speed-reading helper to Readability with Speedability. This works similarly to Spritz, by displaying the words of the webpage in rapid succession.
To use:
1. View a page with Readability (https://www.readability.com/)
2. Click the Speedability icon in the address bar
3. Click play to speed-read the page
Additional controls:
- Use the left and right arrow keys to quickly scan forward and backward.
- Double-click the left and right buttons to skip to the end or beginning